Electro-hydraulically operated mechanical grabs



J. SCHRADER 3,016,260

ELECTRO-HYDRAULICALLY OPERATED MECHANICAL GRABS Jan. 9, 1962 Filed Oct. 12, 1959 WQ/J I J United Swe w 71 ELECTRO-HYDRAULICALLY OPERATED MECHANICAL 'GRABS Jiirgen Sehrader, Peine am Bauhof, Germany, assignor to Norddentsche Schraubenund Mutternwerke A.G., Peine, Germany, a corporation of Germany FiledOct. 12, 1959, Ser. No. 845,805

Claims priority, application Germany Oct. 22,

Claims. (Cl. 294--88) these members.

prising the pump and the electric motor, is mounted above the driving arms, while the operating cylinder for effecting the opening and closing of the grab is located below the pump assembly and between the driving arms of the grab. By reason of the high position of the pump assembly, the center of gravity of the grab is relatively high so that the grab is very top heavy. Consequently, when the grab is lowered onto the load, the grab can easily tip to one side, thus not only impairing the efiiciency but also resulting in the pump assembly, which is mounted to project above the driving arms, being exposed to damage.

It is an object of the invention to overcome these disadvantages by mounting the entire pump assembly, comprising the hydraulic pump and the electric motor as well as the operating cylinder, in the space between the said driving arms.

Another object is to provide a construction of this type having a protective shroud enclosing the pump assembly and through which power is transmitted to the driving arms of the grab.

A further object is the provision of a source of fluid for the hydraulic operating cylinder which is disposed within the driving ring to which the load-engaging arms are pivotally connected.

In the construction of the invention the center of gravity of the grab is lowered substantially, a fact which insures the stability of the grab; moreover the pump assembly and the operating cylinder or cylinders are substantially protected against damage.

Further advantages and features of the invention will be apparent from the following description with reference to the accompanying drawing, which shows in front elevation one embodiment of a grab according to the invention.

The grab consists of load-engaging arms 1, a driving ring 2 to which the load-engaging arms 1 are pivotally connected at 3, and driving arms 4. The pump assembly 5 consists of an electric motor with a high pressure oil pump integrally connected thereto, and is mounted on the driving ring 2 between the driving arms 4. An operating cylinder 6 of conventional construction is mounted above the pump assembly and between the driving arms. The lower end of the cylinder may be supported by the housing of the pump assembly. Driving arms 4 are pivotally connected at their lower ends to the loadengaging arms 1 by means of the pins 12 anchored in a clevis 14. The upper ends of arms 4 are pivotally connected to a connector ring 16 which in turn is fixed to the shaft 18 of the hydraulic cylinder 6.

An oil reservoir 7 lies beneath the pump assembly and wholly or partly within the space below the driving ring 2., an arrangement which at once allows for a reduction in height of the grab and also assists in protecting the oil in the reservoir against contamination.

The power necessary for opening and closing the grab is preferably transmitted by means of the-driving'arms 4 through'a metal casing or shroud 8, which encloses the pump assembly 5 and the operating cylinder 6 and which extends from the upper part of the operating cylinder 6 to the driving ring 2, being fixedly connected to both At the level of the lower part of the operating cylinder 6 the metal casing 8 is provided with a horizontal support 9. This horizontal support 9 is formed with a central opening to receive the operating cylinder 6 and holds the cylinder 6 in a vertical position. Thus, the reacting force against the cylinder during extension is transmit-ted to the driving ring 2 through the casing 8.

Apart from taking up the reaction of the forces occasioned during the opening and closing of the grab, the metal casing 8 serves to protect the pump assembly 5 and the operating cylinder 6 against external damage, and in this respect adds to the protection afforded by the driving arms 4.

In operation, the shaft 18 is extended upwardly as hydraulic fluid from the pump assembly 5 is forced into the lower end of the cylinder. The driving arms 4 are lifted by the connector ring which is fixed to the end of the shaft, and this causes the load-engaging arms 1 to open. After the open arms 1 are placed over a load, the fluid pressure to the cylinder 6 is reversed, causing the shaft 18 to be retracted and the arms 1 to close over the load. The load may be lifted with a crane or the like through a cable 20 fixed to the top of the connector ring.

Modifications of the invention will occur to those skilled in the art without departing from the basic principles of my invention. It is my intention to'cover any modification which may reasonably be included in the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An orange peel mechanical grab characterized by a low center of gravity having a driving ring disposed approximately midway between the upper and lower ends .of the grab, a plurality of downwardly-extending circumferentially-spaced load-engaging arms pivotally connected to said driving ring, a driving arm for each of said loadengaging arms extending upwardly therefrom, a hydraulic cylinder having a movable shaft disposed between said driving arms, connecting means fixed to said movable shaft, and electrically powered means for producing pressurized hydraulic fluid for operating said cylinder interposed between said driving ring and said cylinder to establish a rigid connection therebetween, said driving arms having their upper ends pivotally conected to said connecting means and their lower ends pivotally connected to said load-engaging arms, thereby protecting said cylinder and said electrically powered means from damage during use.

2. The grab of claim 1 which includes a reservoir for hydraulic fluid disposed at least partially within the confines of said driving ring.

3. The grab of claim 1 wherein said means for producing pressurized fluid is an 'electric motor-pump assembly.

4. The grab of claim 3 wherein said cylinder and said motor-pump assembly are enclosed in a protective shroud.

5. A mechanical grab characterized by a low center of gravity having a driving ring, a plurality of downwardly-extending circumferentially-spaced load-engaging arms pivotally connected to said driving ring, a driving arm for each of said load-carrying arms extending upwardly therefrom, a hydraulic cylinder disposed between said driving arms, electrically-powered means for produc- Patented Jan, 9, 1962,

t ing pressurized fiuid for said cylinder interposed between References Cited in the file of this patent said cylinder and said driving ring, said driving arms' being "UNITED E ATE S pivotally connected at their upper ends to the upper end of said hydraulic cylinder and attheir lower ends to said 2188672 Atkinson 1940 driving ring, thereby protecting said cylinder and said 5 2,465,629 1949 electrically-powered means from damage during use, and 2605563 Browmng 1 a shroud enclosing said electrically-powered means having a central cross member embracing the lower end of said cylinder to transmit force from said cylinder to said FOREIGN PATENTS dr v r n 1,158,394 France June 13, 1953 

